When a city floods, humans stack sandbags and raise levees. When a fire ant colony floods, the ants link up to form a literal life raft, such as the one pictured. Now, new research shows exactly how the ants manage this feat.

Engineering professor David Hu and graduate student Nathan J. Mlot at Georgia Institute of Technology had heard reports of ant rafts in the wild that last for weeks. (Watch a fire ant video.)

“They’ll gather up all the eggs in the colony and will make their way up through the underground network of tunnels, and when the flood waters rise above the ground, they’ll link up together in these massive rafts,” Mlot said. Together with Georgia Tech systems-engineering professor Craig Tovey, the scientists collected fire ants and dunked clumps of them in water to see what would happen.

In less than two minutes the ants had linked “hands” to form a floating structure that kept all the insects safe. Even the ants down below can survive this way, thanks to tiny hairs on the ants’ bodies that trap a thin layer of air.

“Even when they’re on the bottom of the raft, they never technically become submerged,” Mlot said.

Read the rest at National Geographic News.